【正文】 ng the development of food supplies. Malthus’s views remain influential today.Malthus claimed that population was growing much more rapidly than Earth’s food supply, because population increased geometrically, while food supply increased arithmetically. F Malthus on the relationships between people and food in future produced by growth rates: 202。v Today: 1 person, 1 unit of foodv 25 years from now: 2 persons, 2 units of foodv 50 years from now: 4 persons, 3 units of foodv 75 years from now: 8 persons, 4 units of foodv 100 years from now: 16 persons, 5 units of foodHe concluded that population growth would press against available resources in every country, unless “moral restraint” produced lower crude birth rates or unless disease, famine, war, or other disasters produced higher crude death rates.2. NeoMalthusiansContemporary geographers have broadened Malthus’s theory to enpass a wide variety of resources, rather than only food. They paint a frightening picture of a world in which billions of people are engaged in a desperate search for food and fuel.Many LDCs have expanded their food production significantly in recent years, but they have more poor people than ever before. Because population growth outpaced economic development, all the economic growth was absorbed simply in acmodating the additional population.3. Debate over how to reduce natural increaseWith death rates controlled, for the first time in history the most critical factor determining the size of the world’s population is the birth rate. Scientists agree that the current rate of natural increase must be reduced, but they disagree on the appropriate methods for achieving this goal.Theoretically, for countries currently in stage 2 of the demographic transition – high growth – natural increase can be reduced in only 2 ways:v Return to stage 1 by raising the crude death rate up to the level of the crude birth rate.v Move to stages 3 and 4 by lowering the crude birth rate to the level of the crude death rate. Few people wish to see the first alternative realized, leaving the second alternative as the only human choice. Scientists and public health officials debate over best means to achieve lower birth rates. One alternative emphasizes reliance on economic development, the other on distribution of contraceptives.252。 Economic development alternativeThis alternative stresses the importance of improving local economic conditions. A wealthier munity has more money to spend on education and health care programs that would promote lower birth rates. With economic conditions improved, women would get better education and therefore better understand their reproductive rights. With improved health care programs, infants would have better chances to live longer. And with the survival of more infants assured, women would be more likely to choose to limit the number of children with more effective methods of contraception.252。 Distribution of contraceptivesThis approach emphasizes the importance of rapidly diffusing modern contraceptive methods. Economic development may promote lower birth rates in the long run, but the world cannot wait around for that approach to take effect. Putting resources into familyplanning programs can reduce birth rates much more rapidly.In LDCs, demand for contraceptive devices is greater than the available supply. Therefore, the most effective way to increase their use is to distribute more of them cheaply and quickly. According to this approach, contraceptives are the best method for lowering the birth rate.Resources and EnvironmentOur prosperity depends on the availability of natural resources and the quality of the environment. Yet economic activities in developed countries, and increasingly in underdeveloped countries, are depleting resources and degrading the environment. What can be done then to effectively manage resources and protect the environment???u Nature and limits of the world’s resources1. Resources and ReservesResources have meaning only in terms of technical and cultural appraisals of nature and must be defined with reference to a particular level of development. Resources include all the materials of the environment that may some day be used under specified technological and socioeconomic conditions.Reserves are quantities of resources that are known and available for economic exploitation with current technologies and at current prices.A financial analogy: reserves are liquid assets, like money in a checking account。 resources are frozen assets or future ine that cannot be used for this month’s car payments. 2. Types of resources and their limits252。 Nonrenewable resources:Finite masses of material, such as fossil fuels and metals。 they are, for all practical purposes, fixed in amount, because they form very slowly over time. Consequently, their rate of use is very important. Large populations with high per capita consumption of goods deplete these resources fastest.252。 Renewable resources:Resources capable of yielding output indefinitely without impairing their productivity。 they include soil, vegetation, air, and water. Renewal is not automatic, however。 renewable resources can be depleted and permanently reduced by misuse. For example, fertile topsoil, destroyed by erosion, can be difficult to restore and impossible to replace.F Resources, both renewable and nonrenewable, are exhaustible. There are limits to growth imposed by the finiteness of the earth – by the fact that air, water, minerals, space, and usable energy sources can be exhausted or overloaded. Existing food, mineral, and energy shortages and areas now beset by deforestation and soil erosion, are among some of the problems human must face. 216。216。 “Tragedy of the mon” (Hardin, 1968)It refers to the way public resources are ruined by the isolated actions of individuals. We appear to be unwilling to use a minimum share of a resource